Biology 1407 Chapter 19 Study Guide: Population Genetics and Evolution

Modern Synthesis Theory: Combines Darwinian natural selection with mendelian genetics, population genetics, and modern biological disciplines.
Microevolution: Changes in allele frequencies within a population over generations.
Macroevolution: Evolutionary patterns and changes above the species level over long time periods.

Natural Selection: Differential reproductive success resulting in phenotypic adaptation and changes in allele frequencies.
Mutation: Random changes in DNA that create new alleles; the ultimate source of genetic variation.
Genetic Drift: Unpredictable allele frequency fluctuations caused by chance events, especially in small populations.
- Founder Effect: Occurs when a few individuals isolate from a larger population to establish a new population.
- Bottleneck Effect: Occurs when a sudden reduction in population size drastically alters allele frequencies.
Gene Flow: Transfer of alleles into or out of a population due to the movement of fertile individuals or gametes.
Nonrandom Mating: Selection of mates based on traits or genetic similarity.
- Assortative Mating: Individuals mate with similar phenotypes.
- Disassortative Mating: Individuals mate with dissimilar phenotypes.

Gene Pool: Total aggregate of all alleles for all loci in a population.
Hardy-Weinberg Equilibrium: Describes a non-evolving population where allele and genotype frequencies remain constant over generations.
Five Assumptions of Hardy-Weinberg Equilibrium:
- No mutations
- Random mating
- No natural selection
- Extremely large population size (no genetic drift)
- No gene flow
Hardy-Weinberg Equations:
- Allele frequencies: $p + q = 1$
- Genotype frequencies: $p^2 + 2pq + q^2 = 1$
- $p$ : Frequency of the dominant allele
- $q$ : Frequency of the recessive allele
- $p^2$ : Frequency of homozygous dominant genotype
- $2pq$ : Frequency of heterozygous genotype
- $q^2$ : Frequency of homozygous recessive genotype

Stabilizing Selection: Favors intermediate phenotypes over extreme phenotypes.
Directional Selection: Favors individuals at one extreme of the phenotypic range.
Diversifying (Disruptive) Selection: Favors individuals at both phenotypic extremes.
Frequency-Dependent Selection: Fitness of a phenotype depends on its commonness in the population.
Sexual Selection: Selection driven by preferences for specific traits in mates.
- Intrasexual Selection: Direct competition among individuals of one sex for mates.
- Intersexual Selection: Choice of mates by individuals of one sex.
Darwinian (Evolutionary) Fitness: Relative contribution an individual makes to the gene pool of the next generation.
Relative Fitness: Contribution of a genotype to the next generation compared to alternative genotypes.

Finch Population Calculation 1:
- Total finches: $210 + 245 + 45 = 500$
- Total alleles: $1000$
- Recessive allele frequency ( $q$ ): $\frac{2 \times 45 + 245}{1000} = 0.335$
- Dominant allele frequency ( $p$ ): $1 - 0.335 = 0.665$
Finch Population Calculation 2:
- Total population: $400$ finches ( $336$ black beaks, $64$ yellow beaks)
- Recessive phenotype frequency ( $q^2$ ): $\frac{64}{400} = 0.16$
- Recessive allele frequency ( $q$ ): $\sqrt{0.16} = 0.40$
- Dominant allele frequency ( $p$ ): $1 - 0.40 = 0.60$
Toadstool Population Calculation:
- Total toadstools: $1007$ ( $14$ plain $tt$
- Recessive genotype frequency ( $q^2$ ): $\frac{14}{1007} \approx 0.0139$
- Recessive allele frequency ( $q$ ): $\sqrt{0.0139} \approx 0.118$
- Dominant allele frequency ( $p$ ): $1 - 0.118 = 0.882$
- Genotype frequencies: $p^2 \approx 0.778$ , $2pq \approx 0.208$ , $q^2 \approx 0.014$
Mice Population Calculation:
- Total mice: $200$ ( $25$ black $tt$ )
- Recessive genotype frequency ( $q^2$ ): $\frac{25}{200} = 0.125$
- Recessive allele frequency ( $q$ ): $\sqrt{0.125} \approx 0.354$
- Dominant allele frequency ( $p$ ): $1 - 0.354 = 0.646$
- Heterozygous frequency ( $2pq$ ): $2 \times 0.646 \times 0.354 \approx 0.457$